The development of light-emitting devices such as organic EL displays has advanced swiftly in recent years. Since light-emitting elements for use in the light-emitting devices as organic EL displays are of the self-emission type, they can be made smaller in thickness and lighter in weight as compared with liquid crystalline light-receiving elements, which require backlight. Moreover, since these light-emitting elements for use in organic EL displays are self-light-emitting ones, they provide high visibility as compared with liquid crystalline light-receiving elements. Organic EL displays, therefore, have the following advantages: they are excellent in visibility, can display images at high speeds, can be driven at low voltages, and can be produced thinner.
Generally, an organic EL display comprises a pair of baseplates respectively having surfaces facing each other, each surface having an electrode formed thereon, and a light-emitting layer sandwiched between the two baseplates, and the light-emitting layer contains a light-emitting material that emits light when voltage is applied to it. The light-emitting layer has a thickness of several hundreds nanometers. Hence, the distance between the two electrodes that face each other is short, and the electrodes easily come in contact with each other. Further, since direct voltage is applied to the light-emitting layer in the organic EL display, impurities readily accumulate on the electrode-electrode interface, which leads to decrease in the operation life of the light-emitting layer.
In order to solve the above problems, there have been developed light-emitting devices that employ light-emitting layers made from liquids produced by electrochemical reactions (see Patent Documents 1 to 3, and Non-Patent Documents 1 and 2, for example). In each one of the light-emitting devices disclosed in Patent Documents 1 and 2 and Non-Patent Documents 1 and 2, the distance between two electrodes is several micrometers or more. Therefore, the electrodes never come into contact with each other. Further, since alternating voltage is applied to light-emitting layers in the light-emitting devices disclosed in Patent Documents 1 to 3 and Non-Patent Document 1, it is possible to solve the problem that the operation life of the light-emitting layers undergo a decrease.    [Patent Document 1] Japanese Laid-Open Patent Publication No. 2007-139899    [Patent Document 2] Japanese Laid-Open Patent Publication No. 2006-301302    [Patent Document 3] Japanese Laid-Open Patent Publication No. 2005-302332    [Non-Patent Document 1] Toshiba Review, Vol. 60, No. 9, p. 33 (2005)    [Non-Patent Document 2] Journal of the Electrochemical Society, Vol. 152 (8), p. A1677 (2005)